纳米CaCO_3对PP/HDPE共混体系微孔发泡过程的影响

聚丙烯(PP)是结晶性聚合物,熔体强度低,发泡性能差。为了提高PP的微孔发泡性能,本文首先将PP与高密度聚乙烯(HDPE)共混,提高其熔体强度;然后在PP/HDPE共混体系中加入少量纳米CaCO3,研究CaCO3的含量对共混体系熔体强度及发泡材料泡孔结构的影响。研究结果表明,纳米CaCO3的加入使体系的熔体强度提高,且随着CaCO3含量的增加,泡孔尺寸减小,泡孔密度增加。然而,加入CaCO3以后,泡孔结构不是很规整,泡孔分布不均匀。     

PP/HDPE/EPDM复合体系微孔发泡实验

聚丙烯(PP)是结晶性聚合物,熔体强度低,发泡性能差.为了提高PP的微孔发泡性能,首先将PP和聚乙烯(PE)共混,然后在PP/PE共混体系中加入少量EPDM,研究EPDM的质量含量对PP/PE共混体系熔体强度和最终泡孔结构的影响.分析机理,寻找能够提高PP熔体强度和改善发泡性能的材料.     

PP/HDPE共混物的黏弹性对泡孔结构的影响

将聚丙烯(PP)分别与两种高密度聚乙烯(HDPE)共混,并采用超临界二氧化碳(SC-CO2)作为发泡剂进行高压釜发泡,得到PP/HDPE发泡材料。同时考察了PP/HDPE熔体的黏弹性,并研究了其对PP/HDPE发泡材料泡孔结构的影响。结果表明:PP与黏弹性低于其本身的HDPE共混时,随着HDPE含量的增加,熔体的黏弹性逐渐减小,其中当HDPE含量为25%时,能够得到均匀细小的微孔结构;PP与黏弹性高于其本身的HDPE共混时,随着HDPE含量的增加,熔体的黏弹性逐渐增大,但所得PP/HDPE发泡材料的泡孔尺寸、孔隙率却不减反增,且泡孔结构完整。     

PP/PS/nano-clay超临界CO_2连续挤出发泡成型研究

以聚丙烯(PP)/聚苯乙烯(PS)/纳米黏土(nano-clay)为研究对象,采用单螺杆连续发泡挤出机系统进行发泡,并用扫描电镜观察了发泡样品的泡孔结构。通过比较泡孔形态、发泡膨胀率、泡孔密度、泡孔直径等分析了PP/PS/nano-clay共混物组分配比对泡孔结构的影响。结果表明,将PP与PS共混,可以改善PP的发泡性能;同时,nano-clay的加入进一步改善了共混体系的发泡性能。随着nano-clay用量的增加,泡孔平均直径减小,泡孔密度增加,当nano-clay用量为5%(质量分数)时,制得了泡孔密度达到2.16×108个/cm3的微孔泡孔塑料。     

不同聚丙烯材料共混的微孔发泡成型研究

聚丙烯(PP)熔体强度低,发泡性能差.将两种PP材料共混来改善PP的发泡性能,研究PP材料性质对共混体系微孔结构的影响.研究表明在各种发泡温度下使用纯PP材料很难制得泡孔结构好的微孔材料,而两种PP材料共混以后再进行微孔发泡,泡孔结构得到了改善.与两种相似熔点和黏度的PP共混材料相比,在高黏度的PP中混入少量的低熔点、低黏度PP时,可以制得泡孔结构更好的微孔材料.研究了共混比例对泡孔形态的影响,并从熔体黏弹性和结晶性能两方面分析了泡孔结构变化的机理.     

发泡用改性聚丙烯的制备和性能研究

通过熔融共混法采用均聚聚丙烯(PP-H)和嵌段共聚聚丙烯(PP-B)制备了PP微发泡基础树脂,并研究了PPH用量对基体树脂发泡后力学性能的影响;同时采用发泡改性剂和成核剂(碳酸钙、滑石粉)对PP微发泡基础树脂进行改性,研究了发泡改性剂和成核剂用量对PP发泡性能的影响。结果表明,随PP-H用量的增加,发泡片材的拉伸强度下降,弯曲强度增加;发泡改性剂提高了PP的熔体强度,随成核剂碳酸钙、滑石粉用量的增加,发泡片材的密度下降,泡孔密度增大,其适宜用量为0.5份(质量份,下同);改性后PP的剪切黏度变小,挤出胀大比增大,相对分子质量分布变化不大;用改性PP制备的微发泡片材的泡孔直径小于50μm,泡孔密度可达10~6个/cm~3。     

纳米蒙脱土、PE对PP/PA6/POE-g-MAH共混体系熔体强度的影响

在PP/PA6/POE-g-MAH三元共混增强聚丙烯熔体强度的基础上,进一步研究了纳米蒙脱土、PE对PP/PA6/POE-g-MAH共混体系熔体强度的影响.研究结果表明:随着蒙脱土PP母料用量的增加,PP/PA6/POE-g-MAH共混体系熔体强度不断降低,而且降低程度比较显著;而随着蒙脱土PA6母料用量的增加,熔体强度先降后升;在PP/PA6/POE-g-MAH共混体系中加入5～20份的LDPE,不能有效地进一步改善其熔体强度,反而降低了熔体强度;加入10份以下的HDPE时,熔体强度改善效果也不明显,但当HDPE的用量较多时(20份时),其熔体强度得到明显提高,可达纯PP的2倍以上.     

聚乳酸/聚丙烯共混体系的制备及其发泡行为研究

采用马来酸酐接枝聚丙烯(MAH-g-PP)作为相容剂,制备了聚乳酸(PLA)/聚丙烯(PP)共混物体系并研究了其发泡行为。采用差式扫描量热仪和旋转流变仪分别研究其热行为和流变行为,采用扫描电镜观察了共混体系的冲击断面形貌及泡孔形态。结果表明,随着MAH-g-PP添加量的增加,共混体系的相容性得到提高,加入PP促进了PLA的结晶,当MAH-g-PP含量达到7%时,PLA的绝对结晶度达到6.07%,同时加入PP提高了PLA/PP共混体系的熔体强度,使其发泡行为得到改善,共混体系的发泡倍率最大可以达到8.1倍。     

化学交联PP/LDPE共混材料的熔体强度及发泡性能

通过化学交联提高聚丙烯/低密度聚乙烯(PP/LDPE)共混物的熔体强度,并对交联PP/LDPE共混物的发泡性能进行了研究.结果表明:交联PP/LDPE共混物熔体在拉伸过程中出现明显的应变硬化现象,熔体强度明显提高;采用交联PP/LDPE共混物可制得泡孔均匀、性能良好的闭孔泡沫材料;随着LDPE含量的增加,交联PP/LDPE共混物的凝胶含量逐渐增加,熔体流动速率(MFR)减小;随着发泡剂用量的增加,交联PP/LDPE共混物泡沫的密度逐渐减小,泡孔孔径略有增大;随着泡沫密度的减小,泡沫材料的拉伸强度、压缩强度及压缩永久变形逐渐减小,拉伸断裂伸长率基本不变.     

HDPE共混PP微孔发泡技术研究进展

介绍了一种用高密度聚乙烯(HDPE)与聚丙烯(PP)共混以改善PP微孔结构的技术,对该技术的研究成果进行了综述性回顾。主要包括结晶度及加工条件对共混体系发泡性能的影响、HDPE熔体流动速率对PP/HDPE共混体系微孔结构的影响。共混发泡技术提高了PP的可发泡性,为解决PP发泡难的问题提供了新方法和新技术。     

Effect of the high‐density polyethylene melt index on the microcellular foaming of high‐density polyethylene/polypropylene blends

The effect of high‐density polyethylene (HDPE)/polypropylene (PP) blending on the crystallinity as a function of the HDPE melt index was studied. The melting temperature and total amount of crystallinity in the HDPE/PP blends were lower than those of the pure polymers, regardless of the blend composition and melt index. The effects of the melt index, blending, and foaming conditions (foaming temperature and foaming time) on the void fractions of HDPEs of various melt indices and HDPE/PP blends were also investigated. The void fraction was strongly dependent on the foaming time, foaming temperature, and blend composition as well as the melt index of HDPE. The void fraction of the foamed 30:70 HDPE/PP blend was always higher than that of the foamed 50:50 HDPE/PP blend, regardless of the melt index. The microcellular structure could be greatly improved with a suitable ratio of HDPE to PP and with foaming above the melting temperature for long enough; however, using high‐melt‐index HDPE in the HDPE/PP blends had a deleterious effect on both the void fraction and cell morphology of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 364–371, 2004     

Microcellular foaming of PE/PP blends

Three different polyethylene/polypropylene (PE/PP) blends were microcellular foamed and their crystallinities and melt strengths were investigated. The relationship between crystallinity, melt strength, and cellular structure was studied. Experimental results showed that the three blends had similar variation patterns in respect of crystallinity, melt strength, and cellular structure, and these variation patterns were correlative for each blend. For all blends, the melt strength and PP melting point initially heightened and then lowered, the PP crystallinity first decreased, and then increased as the PE content increased. At PE content of 30%, the melt strength and PP melting point were highest and the PP crystallinity was least. The blend with lower PP crystallinity and higher melt strength had better cellular structure and broader microcellular foaming temperature range. So, three blends had best cellular structure at PE content of 30%. Furthermore, when compared with PE/homopolymer (hPP) blend, the PE/copolymer PP (cPP) blend had higher melt strength, better cellular structure, and wider microcellular foaming temperature range, so it was more suited to be microcellular foamed. Whereas LDPE/cPP blend had the broadest microcellular foaming temperature range because of its highest melt strength within three blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4149–4159, 2007     

Microcellular foam of polymer blends of HDPE/PP and their composites with wood fiber

In this study, the effects of batch processing conditions (foaming time and temperature) and blend composition as well as the effect of incorporating wood fiber into the blends on the crystallinity, sorption behavior of CO₂, void fraction, and cellular morphology of microcellular foamed high‐density polyethylene (HDPE)/polypropylene (PP) blends and their composites with wood fiber were studied. Blending decreased the crystallinity of HDPE and PP and facilitated microcellular foam production in blend materials. The void fraction was strongly dependent on the processing conditions and on blend composition. Foamed samples with a high void fraction were not always microcellular. The addition of wood fiber inhibited microcellular foaming. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2842–2850, 2003     

Relationship between cell morphology and impact strength of microcellular foamed high‐density polyethylene/polypropylene blends

Polymer blends, such as those resulting from recycling postconsumer plastics, often have poor mechanical properties. Microcellular foams have been shown to have the potential to improve properties, and permit higher‐value uses of mixed polymer streams. In this study, the effects of microcellular batch processing conditions (foaming time and temperature) and HDPE/PP blend compositions on the cell morphology (the average cell size and cell‐population density) and impact strength were studied. Optical microscopy was used to investigate the miscibility and crystalline morphology of the HDPE/PP blends. Pure HDPE and PP did not foam well at any processing conditions. Blending facilitated the formation of microcellular structures in polyolefins because of the poorly bonded interfaces of immiscible HDPE/PP blends, which favored cell nucleation. The experimental results indicated that well‐developed microcellular structures are produced in HDPE/PP blends at ratios of 50:50 and 30:70. The cell morphology had a strong relationship with the impact strength of foamed samples. Improvement in impact strength was associated with well‐developed microcellular morphology. Polym. Eng. Sci. 44:1551–1560, 2004. © 2004 Society of Plastics Engineers.     

CHARACTERIZATION OF MICROCELLULAR FOAMED POLYOLEFIN BLEND COMPOSITES WITH WOOD FIBER

The effects of wood fiber content on the void fraction, cell morphology, and notched Izod impact strength of microcellular foamed HDPE/PP blend composites with wood fiber were studied. The influence of wood fiber content on the carbon dioxide adsorption and desorption in the samples was also examined. Adsorption of carbon dioxide decreased with increased wood fiber content. Gas diffusion rates were faster as wood fiber content increased. The void fraction decreased dramatically when wood fiber was introduced in the blend. Environmental scanning electron microscopy (ESEM) was used to investigate the effects of wood fiber content on cell morphology. The 30:70 HDPE/PP polymer blend without wood fiber resulted in a high void fraction, with a uniform and well-developed microcellular structure, but when wood fiber was introduced, a uniform and well-developed microcellular structure could not be produced. The effects of foaming on Izod impact strength were dependent on wood fiber content.     

氯化聚乙烯对聚丙烯／滑石粉复合材料性能影响的研究

本文对ＰＰ／Ｔａｌｃ二元复合材料和ＰＰ／ＣＰＥ／Ｔａｌｃ三元复合材料的物理机械性能，流变性能，熔体流动性能和形态结构进行初步研究。研究结果表明，ＣＰＥ作为第三组分加到ＰＰ／Ｔａｌｃ二元复合材料体系中，对其综合性能并未提高，似乎有下降的趋势。这表明Ｔａｌｃ填充ＰＰ是一个较为理想的体系，无需再加入ＣＰＥ这类高分子抗冲改性剂作为第三组分。并从形态结构进行了阐述。     

Morphology and Properties of Polypropylene Foaming Sheet with Alternating Multilayered Structure

In this work, the foaming sheet was designed as alternating multilayered foam/film structure of foaming layers and film layers. The foaming layer contained polypropylene (PP)/high density polyethylene (HDPE)/Talc ternary composites. The film layer contained PP only. The rheological data showed that the melt elasticity of PP was obviously improved by the addition of HDPE and talc. The results exhibited that the alternating multilayered structure was well kept and hardly influenced by the foaming layers, and then the mechanical properties were obviously improved. The cell in the alternating multilayered sheet with 16 layers was smaller and more homogenous than that in pure PP foaming sheet.     

剪切对PP/HDPE共混体系微孔发泡成型的影响

在熔体流动方向垂直叠加一个轴向脉动剪切,研究转子转动产生的剪切和轴向脉动剪切对PP/HDPE共混体系微孔发泡成型的影响。研究结果表明,随着转子转速增加,泡孔尺寸减小,气泡成核密度增大。但是转子转速过快,泡孔沿剪切的方向被拉长,泡孔取向严重,泡体质量变差。在熔体流动方向垂直叠加一个轴向脉动剪切以后,泡孔的取向现象减小,泡孔逐渐趋于圆形,泡孔结构得到改善。而且随着振动振幅和频率的增加,泡孔直径减小,泡孔密度增加。